Many mobile machines have one or more electric propulsion motors. Some mobile machines have one or more generator units that generate electricity, a plurality of electric propulsion motors, and a power-transfer system for transferring electricity from one or more of the generator units to one or more of the electric propulsion motors. Some such electric machines have a plurality of the electric propulsion motors connected to the power-transfer system in series, which may provide certain benefits. Other electric machines have all of their electric propulsion motors connected to the power-transfer system in parallel, which may provide other benefits.
Leaving the electric propulsion motors connected to the power-transfer system in the same manner at all times may involve compromises. In some circumstances, the benefits associated with connecting electric propulsion motors in series may provide a greater performance advantage than the benefits associated with connecting the electric propulsion motors in parallel. In other circumstances, the benefits associated with connecting the electric propulsion motors in parallel may provide a greater performance advantage than the benefits associated with connecting the electric propulsion motors in series.
U.S. Pat. No. 2,658,174 to Warrick et al. (“the '174 patent”) discloses automatically switching between series and parallel connection of traction motors during operation of a locomotive. The '174 patent discloses an electric generator, two pairs of electric propulsion motors, and a circuit for supplying electricity from the electric generator to the electric propulsion motors. The circuit includes a pair of switches operable to connect each pair of electric propulsion motors in series and a pair of switches operable to connect each pair of electric propulsion motors in parallel. For all operating circumstances, the '174 patent discloses one method of controlling whether each pair of electric propulsion motors is connected in series or in parallel. Specifically, the '174 patent discloses that a control relay always triggers a transition between series connection and parallel connection in response to one particular combination of voltage and electric current supplied by the electric generator.
Although the '174 patent discloses automatically switching between series and parallel connection of electric propulsion motors during operation, certain disadvantages persist. For example, using the same strategy in all circumstances to control whether the traction motors are connected in series or parallel may involve compromises.
The mobile machine and methods of the present disclosure solve one or more of the problems set forth above.